2 - oestrus cycle

Question 1

regulation of reproductive hormones

Answer 1

GnRH/gonadotropin releasing hormone - hypothalamus
anterior pituitary - LH and FSH released
gonad - progesterone and oestrogen
controlled by negative feedback

Question 2

what drives foliuclar development

Answer 2

hypothalamus

Question 3

example of positive feedback of ovulation

Answer 3

high levels of estrogens from almost mature follicle stimulate release of more GnRH and LH
GnRH promotes release of FSH and more LH - hypothalamus
LH surge brings about ovulation - anterior pituitary

Question 4

what is the corpus luteum

Answer 4

mature graafian follicle becomes corpus luteum - temporary structure essential for establishing and maintaining pregnancy in females

Question 5

what happens after 14 days if 2degrees oocycte not fertilised

Answer 5

corpus luteum undergoes luteolysis - stops secreting progesterone and degenerates into coprus albicans - mass of fibrous scar tissue

Question 6

what hormone inhibits GnRH

Answer 6

progesterone

Question 7

what hormone drives the ovarian cycle

Answer 7

GnRH

Question 8

reflex ovulators

Answer 8

GnRH pulse generator not sensitive enough to the high oestrogen to induce an LH surge - additional inputs put in place during copulation
in absence of coitus - only have follicular phase
need additional inputs to the brain to induce ovulation
stretch inputs from vagina and sensory inputs all combine to increase GnRH = increases LH - initiates ovulation and CL

Question 9

oestrus cycles of the mare

Answer 9

seasonal long day breeders
21 day cycle
oestrus - 5 days
ovulate - 24-48 hours before oestrus

Question 10

oestrus cycle of the sheep

Answer 10

17 day cycle
oestrus lasts 30 hours
ovulates 20-25 hours from start of oestrus
seasonal polyoestrus
short day breeders

Question 11

oestrus cycle of cow

Answer 11

not seasonal
21 day cycle
oestrus cycle lasts 18 hours
ovulates 20-30hours from start of oestrus

Question 12

what is luteolysis

Answer 12

loss of progesterone secretion by the CL followed by loss of luteal tissue mass

Question 13

luteolysis in ruminants

Answer 13

oxytocin secreted from CL and posterior pituitary
action depends on presence/absence oxytocin receptor
oxytocin receptors appear on endometrium in late luteal phase

Question 14

role of prostoglandin in luteolysis

Answer 14

causes regression of the CL in ruminants horses and pigs